The present invention relates to a combine harvester having on the one hand a device for discharging husks from a sieving unit on the combine harvester, said husk discharging device being arranged downstream of the sieving unit and having at least one fan which is rotatably mounted in a casing with at least one husk discharge opening and, on the other hand, a device for chopping of straw from a straw shaking unit on the combine harvester, said straw chopping device being arranged downstream of the straw shaking unit and the husk discharging device and having a rotating cutting rotor in a casing for chopping the straw, said casing having an inlet for the unchopped straw and an outlet for the chopped straw, a control device being arranged between the husk discharging and straw chopping devices which is movable between a first position, in which it shuts the inlet of the casing of the straw chopping device to bypass the straw chopping device and allow laying of strings of the unchopped straw, and a second position, in which it uncovers the inlet to allow chopping of the straw.
The harvest residues forming in the threshing in the combine harvester normally consist of husks and straw from such crops as wheat, barley, oats and rye, but may also come from, for instance, different kinds of oil plants and maize, sunflowers etc. which have fairly large and stiff plant parts. In the following description however, the terms husks and straw will be used throughout for the sake of simplicity and clarity.
Modern combine harvesters become larger and larger with broader and broader cutting tables which in themselves are significantly broader than the width of the actual harvester. In threshing, large amounts of smoke and dust arise in the vicinity of the harvester, which is a great problem in respect of the engine and above all the great risk of fire. To reduce this risk, it is important that as large amounts as possible of the residues of harvest consisting of straw and husks be spread as far outwards backwards from the harvester as possible.
The husk discharging device connected to the sieving unit of the harvester is roughly as wide as the actual harvester and should normally after threshing spread the husks sideways and rearwards over an area which essentially corresponds to the width of the cutting table. The straw chopping device arranged downstream of the husk discharging device and connected to the straw shaking unit of the harvester is also approximately of the same width as the actual harvester and should normally after threshing cut the straw into small pieces and spread the cut straw over an area after the harvester which essentially corresponds to the width of spreading the husks. After the spreading of the husks and the cut straw as described above, the husks together with the straw are as a rule ploughed back into the ground.
If, for various reasons, it is desirable not to cut the straw in the straw chopping device but instead to lay strings of straw after the combine harvester for subsequent collection and suitably baling to be used, for instance, as feed, bedding etc. this can easily be done by moving the movable control device to its first position, and vice versa to its second position for cutting of the straw.
Moreover, it is previously known per se in a similar combine harvester to blow the husks from the sieving unit directly into the straw chopping device through its inlet to be mixed with the straw that is to be chopped. If the straw would then instead be laid in strings there is no possibility of spreading the husks sideways and rearwards.
The main object of the invention is that the operator of the combine harvester, in consideration of, inter alia, the risk of fire, the type of crop to be harvested, the moisture content of the crop and how the crop residues are to be treated etc, should himself be able to choose/determine whether the husks and the straw are to be spread separately or jointly, no matter whether the straw is to be chopped or laid in strings.
A further object of the invention is to enable this freedom of choice with technically and functionally simple and quick means.
According to the invention, these and other objects are achieved in a manner which is as simple as ingenious by the husk discharge opening in the fan casing of the husk discharging device being alternatingly settable between a first position where the husks are made to spread over the substrate, and a second position where the husks are mixable into the unchopped straw.
If the straw is to be laid in strings, the mixing of the husks into the straw which is to be laid in strings can preferably be carried out with the control device in its first position and the husk discharge opening in its second position. However, if the straw is to be chopped, the mixing of the husks into the straw that is to be chopped may be carried out with the control device and the husk discharge opening in their second positions, whereupon the husks are chopped and spread together with the chopped straw.